Hi A more significant issue with the output of the TBolt for direct microwave multiplication is the spurs on the output. When multiplied up to > 1 GHz, these are going to be a major issue. There are a lot of conventional techniques for taking care of this. If you have not already employed them, they are probably the first thing to take a look at.
For cross correlating signals, the time sync of the signals is at least as important as the frequency error. As with phase noise, there are a lot of ways to address this. Most of the “better frequency” suggestions here are also “worse time” suggestions. Bob > On Sep 13, 2016, at 1:04 PM, Mike Baker <[email protected]> wrote: > > Hello, Time-Nutters-- > > Full disclosure-- I am a complete newbie at understanding the > intricacies of generating a really stable, low phase noise, accurate > frequency reference for microwave reception up around the 8 GHz > DSN (Deep Space Network) band. I have been following the back > and forth comments on the Time-Nuts list about improving the > Trimble T-bolt's 10 MHz output but confess that most of it is pretty > much deeper technical voo-doo than I am comfortable with. > > I have been following the exploits of a group of folks around the > world who receive the incredibly weak signals from space probes > such as Juno. The idea is to detect the signals and then deduce > and confirm what probe is being detected by analyzing its doppler > and orbital characteristics. > > This is being done at around 8.4 GHz with relatively small dishes of > under 8-ft diameter. Part of the magic that permits identifying > signals so far below the noise floor is the ability to use very narrow > bandwidth; as little as couple of Hz or even more narrow than that. > In order to do this a really accurate/stable/low phase-noise frequency > reference is needed. > > I have been running a Trimble T-bolt 24/7/365 on Lady Heather > for around 5 years but have just started to take note of comments > on this list that the T-bolt is not really very good as a source to > phase-lock to for producing super narrow bandwidths of only one > or two Hz at 8 GHz. The comments I hear on the DSN space-probe > hunters chat-list is that obtaining a really high quality freq reference > is one of the big obstacles to success at this game. > > My workbench test gear is limited to a pair of spectrum analyzers > (Tek 495AP and a Tek 494AP) and an HP 8714ES Vector Network Analyzer. > John Miles was the source for the Tek 495 spec-analyzer a few years ago. > > John-- you might recall the check I sent you for the Tek495AP that > got lost...? Did it ever turn up? > > Accordingly, what possible options might I have open to obtaining > a decent 10 MHz frequency reference for working up at the 8 GHz > DSN band? Any feedback on this will be much appreciated! > > Mike Baker > Gainesville FL > (Micanopy, actually, about 12 miles south of Gainesville) > **************************** > > As a side note, I built a tracking downlink to receive and display > the digital imagery from the environmental low-earth polar orbit > satellites several years ago. This HRPT data comes down at around > 1.7 GHz. The USA, Russia, Japan and China each have 2 to 4 of these > low-earth orbit birds (100 minute orbits) and one of them passes > overhead every other hour or so. I have a lot of trees around my > house and these limit my open-sky area but I can still start to get > solid reception when the birds pass over Cuba and drop-off when > they are over Tennessee. > > Photos of my home-brew tracking station can be seen here in the > back yard behind my workshop building: > > *http://tinyurl.com/j676ap2* > > And some low-res screen-grabs of false-color infrared earth surface > images here: > > http://tinyurl.com/jsv323l > > *http://tinyurl.com/jvxkc9g > > **http://tinyurl.com/hbo886y* > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
